Baseball and softball bats, hereinafter referred to simply as “baseball bats” or “bats”, are today typically made solely from aluminum alloys, or aluminum alloys in combination with composite materials (hybrid bats), or most recently solely from composite materials (with the exception of solid wooden bats for the Major Leagues). Such bats are tubular (hollow inside) in construction in order to meet the weight requirement of the end user, have a cylindrical handle portion for gripping, a cylindrical barrel portion for hitting, and a tapered mid-section connecting the handle and barrel portions.
When aluminum alloys initially replaced wooden bats in most bat categories, the bats were formed as a single aluminum member, that is, they were made in a unitary manner as a single-wall aluminum tube for the handle, taper, and barrel portions. Such bats are often called single-wall aluminum bats and were known to improve performance relative to wooden bats as defined by increased hitting distance. More recently (in the mid 1990's), improvements in bat design largely concentrated on further improving bat performance. This was accomplished by thinning the barrel wall of the single-wall bat frame, and adding inner or internal, and/or outer or external secondary members extending along the entire barrel length. These members are often referred to respectively as inserts or sleeves; while the main member is often referred to as a body, shell or frame. Such bats, constructed of metallic and/or composite materials are often called double-walled bats or multi-walled bats in the case of more than two walls resulting from two or more secondary members.
Such double-walled and multi-walled tubular bats generally attained improved performance in terms of hitting distance by reason of the improved deflection that is characteristic of a multilayer barrel wall. The efficient batting of a ball is maximized by minimizing plastic deformation, both within the bat and within the ball. Ideally, during the bat-ball collision, the barrel wall of the bat should not deform beyond its elastic limit. In a multi-walled bat, having two or more members along the entire barrel length, the barrel portion is allowed to elastically deflect or flex more upon ball impact, which propels the ball faster and further than prior art single wall bats.
The scientific principle governing improved tubular bat performance is bending theory. When a ball impacts a tubular bat it has kinetic energy that must be absorbed by the bat in order to stop the ball. The bat stores most of this energy by flexing, which results in various vibrational bending modes. The ball as well deforms in a hoop direction. The first or fundamental hoop bending mode of a tubular bat gives rise to what is commonly referred to as a tubular bat's trampoline effect, which can increase bat performance. The peak of this first bending mode is often referred to as being approximately concurrent with the bat's sweet spot. After the ball is stopped, the bat returns the energy it has stored by rebounding and sending the ball towards from where it came. The more the bat barrel or striking portion deforms upon ball impact without failing (denting or breaking) or experiencing plastic deformation, the lower the energy loss and the greater the energy returned to the ball from the bat as the tubular bat barrel portion returns to its original shape following impact.
To allow the bat barrel portion to deform requires lowering the radial stiffness of the barrel portion. The prior art double-walled and multi-walled tubular bats have traditionally accomplished this by thinning the main member of the barrel portion and adding thin secondary member insert(s) and/or sleeve(s) which are not bonded to the main member, but which generally extend throughout the full length of the barrel portion. Such inserts and sleeves are not coupled to the barrel wall portion of the frame, and these two contacting components may slide with respect to each other in the same manner as leafs within a leaf spring. The resultant lowered radial stiffness along the barrel portion length permits the barrel wall to deflect elastically.
U.S. Pat. No. 5,415,398 is an example of a multi-walled bat that discloses use of a frame and an internal insert of constant thickness running full length of the barrel portion of the bat in a double-wall construction.
Other similar bat designs are defied in U.S. Pat. No. 5,303,917, which discloses a two-member bat of thermoplastic and composite materials and U.S. Pat. No. 5,364,095, which discloses a two-member bat consisting of an external metal tube and an internal composite sleeve bonded to the inside of the external metal tube and running full length of the barrel portion of the bat.
U.S. Pat. No. 6,251,034 discloses a polymer composite second tubular member running throughout the full length of the barrel portion of the bat with the members joined at the ends only of the barrel portion with the balance of the composite member freely moveable relative to the primary member. U.S. Pat. No. 6,440,017 also discloses two member bats with an outer sleeve and inner shell of constant thickness running full length of the barrel portion. Other references include U.S. Pat. No. 6,287,222, U.S. Pat. No. 6,461,260, U.S. Pat. No. 6,425,836, and U.S. Publication 2002/0094892.
In all of the above-noted multi-walled tubular bats, the bat secondary member, or insert, extends along the entire frame barrel length, has constant diameter and thickness, resulting in uniform cross-sectional geometry along the secondary member length. Also, the bat members are not joined, except at their ends, in order to reduce radial stiffness of the barrel portion to improve bat performance. Also, in all cases, the radial stiffness of the barrel portion is uniform or constant throughout the full length of the barrel portion of the bats.
While the prior art single-wall, double-walled and multi-walled tubular bats have demonstrated improved performance as claimed, various regulatory bodies have raised safety concerns regarding improved performance bats and thus, some have established maximum performance standards for various categories of baseball bats under their jurisdiction. As a result, manufacturers of baseball bats are required to pass various controlled laboratory tests, such as, BBF (batted ball performance), BBS (batted ball speed), BBCOR (batted ball coefficient of restitution), all of which are designed with the intent of limiting bat performance as measured by hit distance. Further, for a given bat category (e.g. slow pitch softball), there may be two or more regulatory bodies, each of which may establish a different standard. Further, any of the regulatory bodies may change their standard from time to time. Such new or changed regulations are extremely problematic, costly, and disruptive for both manufacturers and players.
It is generally not desirable to lower the performance of a bat by simply increasing the thickness of the barrel wall of one or more of the barrel members along its full length. Lowering the performance of the bat by merely increasing the wall thickness can increase weight such that the finished bat weight objective is exceeded. On the other hand, it is desirable while meeting lowered bat performance standards, to improve player performance as opposed to bat performance by selectively locating the bat's sweet spot along its length and/or by creating a bifurcation, or two or more sweet spots along the bat barrel length.
Therefore, what is needed is a simple low-cost, low-weight-added invention to selectively, by design, locate the bat sweet spot along the bat barrel length or to create two or more sweet spots along the barrel length, which improves player performance while meeting mandated bat performance standards.
The sweet spot of a bat is generally the portion of the barrel, which when struck by the ball, provides maximum batting performance. It is the location on the barrel at which the bat-ball collision occurs with maximum efficiently and with the transmission of minimum vibration through the handle to the hands of a user. Maximum bat performance, as measured by hit distance, occurs at the middle or peak of the sweet spot area. The sweet spot is located approximately at the fundamental hoop mode's maximum amplitude, the antinode, and is located generally midway along the barrel portion of prior art tubular bats. It is highly desirable to provide improved player performance bats with either the sweet spot selectively located along the bat barrel length away from the barrel mid-point, or to create two or more sweet spots along the tubular bat barrel length. Both of these designs can improve player performance as opposed to bat performance, which is an objective of the present invention. Further, bats of the present invention having one or more a thin, lightweight internal diaphragms, besides improving player performance, meet regulated bat performance standards while providing a vibration free, soft feel and unique sound upon contact with a ball.
U.S. Publication 2005/0070384 addresses the creation of a larger sweet spot region by varying radial stiffness along the barrel length by adding a ring stiffener, or by changing fibre properties along the barrel length, or by thickening the barrel wall generally in the area of the sweet spot.
U.S. Publication 2011/0152015 addresses the objective of controlling bat performance by employing a central tube positioned coaxially within the barrel joined at the barrel end cap and including at least one restrictive member capable of limiting the bat performance.
U.S. Pat. No. 6,949,038 purports to achieve an improved sweet spot characteristic by providing a secondary member, located either inside or outside the barrel of a standard bat frame, wherein the secondary member has a constant outside diameter with an internal wall whose thickness increases while proceeding from its ends respectively inwardly towards the opposing ends. Generally, this thickening is shown to increase to a maximum around the mid-portion of the length of the secondary member. In FIG. 12, this thickness is shown to practically decrease the mid-portion of the length of the secondary member, providing two laterally placed regions of maximum thickness on either side of the mid-portion.
While prior constructions represent different means of limiting or reducing bat performance and/or achieving an enlarged sweet spot of a baseball bat, one objective is to improve player performance, as opposed to bat performance, by selectively relocating the sweet spot area or creating a bifurcation of the sweet spot resulting in two or more separate sweet spot areas along the bat barrel length. To achieve this objective, bats according to embodiments of the present invention have one or more thin lightweight diaphragms internally placed and selectively fastened within the bat's internal cavity.